The material below is Open Game Content from a 3PP Source
Knotted Strap: This coarse bit of leather, drawn into a tight loop, often commemorates tasks involving defending a wild place from encroaching civilization. A halfling who uses it while casting shillelagh can cast the spell on a sling to give it the abilities of a +1 sling. Ammunition launched from this sling deals damage as if fired by a Large creature (bullets 1d6, stones 1d4) regardless of the halfling’s current size. If not wielded by the caster, the weapon behaves as if unaffected by this spell.